The next generation of wireless (e.g., cellular) communication technology standards improve over the previous generation's data throughput. It is expected that the so-called fifth generation (5G) wireless communication systems and networks will dramatically (e.g., about twice as much) increase the data throughput of the previous generation.
Existing wireless communication systems and networks (including current generations) employ duplexing. Namely, either frequency division duplex (FDD) or time division duplex (TDD) has been used for separate transmission and reception. In FDD and TDD, transmitted signal does not interfere with received signal due to a separate use of frequency and time resources respectively. Therefore twice the amount of frequency and/or time are used in current duplexing systems compared to in-band full-duplex systems (IBFD). It seems possible to double data throughputs by simultaneous transmission and reception in the same frequency band at the same time.
In-band full-duplex (IBFD) operation has emerged as an attractive solution to increase the data throughput of wireless communication systems and networks. With IBFD, a wireless device (i.e., node) transmits and receives simultaneously in the same or common frequency band. However, one the biggest practical impediments to IBFD operation is the presence of self-interference (i.e., the interference caused by an IBFD node's own transmissions to its desired receptions).
The self-interference impediment to IBFD operation has been addressed by several conventional antenna designs. For example, one conventional approach is called echo cancellation. In this approach, a single antenna is used for both transmission and reception. That antenna is connected to a circulator. The circulator interconnects three different elements: antenna, transmitting (TX) radio frequency (RF) subsystem, and receiving (RX) RF subsystem.
While this arrangement accomplishes the IBFD operation, there is a signal leakage from the TX RF subsystem to the RX RF subsystem due to a relatively low isolation level (e.g., ˜20 dB) between the TX and RX port in the circulator. In addition to the TX signal leakage, the TX signal is reflected due to impedance mismatch at the antenna port. This reflection may dominate the desired RX signal at the RX RF subsystem. Furthermore, as wireless commination components go, a circulator is relatively large and heavy because of its magnets.
Another conventional approach utilizes two separate antennas. The antenna pairs have a high isolation level (e.g., ˜40 dB) with a relatively large separation and each antenna is dedicated to either signal transmission (TX) or reception (RX). While this dual-antenna approach eliminates the heavy and large circulator, it introduces new problems. The primary problems of this dual-antenna approach are space and complexity. Two separate and isolated antennas require more space because there are twice as many antennas and those antenna must be physically spaced from each other sufficiently enough to reduce interference therebetween.
The Detailed Description references the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.